Any nonzero number raised to the zeroth power is 1, so `28^0=1.` This is a definition and it's made so that certain patterns hold and the laws of positive exponents carry over to zero and negative exponents.

Consider this:

`28^3=21952`

`28^2=784=21952/28`

`28^1=28=784/28`, so the pattern suggests defining

`28^0=1=28/28.`

Another way to view it:

For positive exponents, `x^m/x^n=x^(m-n).` Using this we get

`1=28^1/28^1=28^(1-1)=28^0.` Again, this suggests that we should define `28^0` to be 1. This same reasoning can be used to define negative exponents in a consistent way.